A control unit in general is a central (or sometimes distributed but clearly distinguishable) part of the machinery that controls its operation, provided that a piece of machinery is complex and organized enough to contain any such unit. One domain in which the term is specifically used is the area of computer design. In the automotive industry, the control unit helps maintain various functions of the motor vehicle.

The rest of this article describes control unit in terms of computer design. There is no further article on other uses under this lemma as yet. (Disambiguation and/or integration of this article in Computer with respective linkage—and retention/creation of a more broad-sense article—may be appropriate.)

In computers, the control unit was historically defined as one distinct part of the 1946 reference model of Von Neumann architecture. In modern computer designs, the control unit is typically an internal part of the CPU with its overall role and operation unchanged.

General operation

The outputs of the control unit control the activity of the rest of the device. A control unit can be thought of as a finite state machine.

The control unit is the circuitry that controls the flow of data through the processor, and coordinates the activities of the other units within it. In a way, it is the "brain within the brain", as it controls what happens inside the processor, which in turn controls the rest of the PC.[vague]